Apparatus for radiation polymerization

ABSTRACT

An elongated radioactive source of gamma radiation is used in initiating polymerization in a polymerization reactor. The elongated source rod is axially movable within the reactor so that its end terminates at any desired location within the reactor which will have polymerization processes initiated. This in turn adjusts the production rate of the reactor. A servo system is connected to drive the radioactive source rod to maintain a constant production rate. The radioactive rod may be divided into two or more parallel rods which are independently movable in order to provide any desired profile for the intensity of the radiation source.

Sept. 18, 1973 G. M, PLATZ ET AL APPARATUS FOR RADIATION POLYMERIZATION5 Sheets-Sheet f;

Filed Jan. 16, 1970 Sept. 18, 1973 G. M. PLATZ ET AL 3,759,811

APPARATUS FOR RADIATION POLYMERIZATION [ii /477d wrin /77 z x UnitedStates Patent Int. Cl. Blllj 1/10 U.S. Cl. 204-193 Claims ABSTRACT OFTHE DISCLOSURE An elongated radioactive source of gamma radiation isused in initiating polymerization in a polymerization reactor. Theelongated source rod is axially movable within the reactor so that itsend terminates at any desired location within the reactor, therebyadjusting the effective volume within the reactor which will havepolymerization processes initiated. This in turn adjusts the productionrate of the reactor. A servo system is connected to drive theradioactive source rod to maintain a constant production rate. Theradioactive rod may be divided into two or more parallel rods which areindependently movable in order to provide any desired profile for theintensity of the radiation source.

This application is related to copending application Ser. No. 11,248,filed Feb. 13, 1970, in the name of Gerald M. Platz et al., entitled,Stirrer and Radioactive Source for Polymerization Reactor, assigned tothe assignee of the present invention.

This invention relates to the control of a radioactive source forradiation-induced polymerization reactors and more particularly relatesto the adjustable control of an elongated source rod of gamma radiationwithin a polymerization reactor.

The above-noted copending application Ser. No. 11,248 describes a novelradiation reactor in which an elongated rod extending along the axis ofthe reactor serves as the radiation source.

In accordance with the present invention, the position of the radiationsource is controlled in location within the interior of the radiationreactor in order to control the volume within the reactor which isexposed to the effective radiation of the source. By this means theproduction rate of the reactor may be held constant as by sensing thetemperature of the reaction mixture with fast acting thermocouples andthen adjusting the fraction of the reactor volume that is beingirradiated to maintain constant temperature. This novel control reduceslarge fluctuations in production rate that would otherwise occur.

While the novel control of the present invention is shown forapplication to the polymerization of ethylene, it will be understood tothose skilled in the art that the novel control process can be appliedin general to any continuous exothermic reaction initiated by highenergy radiation and operated adiabatically. Moreover, the movement ofthe radiation rod can be achieved either manually or automaticallythrough a suitable servo mechanism.

In accordance with another feature of the invention, the radiationsource rod is divided into two or more parallel rods which areindependently axially movable thereby to obtain an adjustable profilefor the source intensity of the reactor along the axis thereby. Each ofthe rods may be controlled by respective remotely operating servomechanisms or may be manually controlled. By profiling the intensity ofthe radiation source in this manner, novel temperature profiles can beobtained along the reactor axis which can be matched to the desiredprofile for the production of various types of polymers. This profilecan be a gradually-sloping profile or a step-shaped profile dependingupon the need for the production of a particular polymer.

3,759,811 Patented Sept. 18, 1973 Accordingly, a primary object of thisinvention is to provide a novel control process and structure fornuclear radiation and polymerization reactors.

Another object of this invention is to maintain a constant productionrate by varying the location of a radiation source in a polymerizationreactor.

Yet another object of this invention is to provide a novel elongatedradiation source consisting of a plurality of axially movableradioactive rods which can be adjusted in order to adjust the profile ofthe intensity of the source along the axis thereof.

A still further object of this invention is to provide the control ofproduction rate in a continuous exothermic adiabatic reaction.

These and other objects of this invention will become apparent whentaken in connection with the drawings, in which:

FIG. 1 schematically illustrates the reactor system of the invention asmounted in a building.

FIG. 2 is a schematic cross-sectional view of the reactor configurationfor the reactor system of FIG. 1.

FIG. 3 is a side plan view of the actual reactor constructionschematically illustrated in FIG. 2.

FIG. 4 is a top view of FIG. 3.

FIG. 5 is a detailed cross-sectional view taken along the axis of thereactor of FIG. 3 with the major body of the stirrer drum removed toexpose the radioactive source container.

FIG. 6 is a cross-sectional view similar to FIG. 5 and illustrating thestirrer drum in detail.

FIG. 7 is a cross-sectional view of FIG. 6 taken across the section line77 in FIG. 6.

FIG. 8 is a cross-sectional view of FIG. 6 taken across the section line88 in FIG. 6.

FIG. 9 is a cross-sectional view of FIG. 6 taken across the section line99 in FIG. 6.

FIG. 10 is a cross-sectional view of a single paddle section of thestirrer drum of FIG. 6 taken across the section line 1010 in FIG. 6.

FIG. 11 schematically illustrates the reactor of the foregoing figuresto demonstrate the operation of the control of the system.

FIG. 12 shows a function of the various relationships used incalculating the operation of the control operation.

FIG. 13 graphically illustrates the radiation intensity (which isrelated to production rate) of the reactor for the radiation rod inthree different positions.

FIG. 14 is similar to FIG. 2 but shows the use of a plurality ofparallel radioactive source rods.

FIG. 15 is a cross-sectional view of FIG. 14 taken across the sectionline 1515 in FIG. 14.

Referring first to FIG. 1, the reactor is schematically illustrated asbeing supported on a ground floor 20 and extending to an upper floor 21.The reactor assembly includes a large cylindrical stainless steel shell22 which could have a diameter, for example, of 10 feet and a suitableheight. The stainless steel shell 22 could be inserted in a pit which islined with the stainless steel shell, if desired. The stainless steelshell 22 will have any desired thickness necessary for suitablestructural strength. Radioactive shielding is provided by concrete, orthe like. Alternatively, the entire reactor can be placed in a pitwithin a suitable facility.

Shell 22 is then filled with deionized water to the dotted line level 23where the deionized water serves to shield radioactive pencils which canbe stored in water when the reactor is not in use, as will be described.The water level above ground may be about 15 feet. A work platform 24,which could be a grating, is then secured above the water level 23 andthe main reactorstructure 25 is supported above the work platform 24 andwater level 23 b suitable mechanical supports (not shown).

The entire reactor assembly will be contained in a suitable facilityprovided with all necessary safety precautions which are well known whenhandling radioactive materials. The support for the reactor may includethe schematically illustrated removable support rack 26 which is shownat the upper floor level and surrounded by a suitable water curb 27. Twohollow vent stacks 28 and 29 of a standard type then communicate withthe interior of reactor in any desired manner so that the high pressurewithin reactor 25 can be exhausted to the exte rior of the facility inthe event of the build-up of excessively high pressures within reactor25.

An operating motor 30 is mounted within the reactor 25 for driving astirrer drum within the reactor 25. Polymerization reactions withinreactor 25 are initiated by an elongated radioactive pencil or rod 31which is mounted on lift rods 32 and 33 which are movable in thedirection shown by arrows 34 and 35 to move the pencil source 31coaxially within the interior of reactor 25. The radioactive rod 31 maycontain a plurality of pencils, each about 1 foot long which are stackedend to end, with each of the individual pencils containing a suitablesource of gamma radiation, such as wires or pellets of Cobalt 60. Suchmaterials are commercially available.

In one embodiment of the invention, a sufficient number of such pencilsare stacked to a length of about 15 feet, with the reaction zone withinreactor 25 also being about 15 feet. Obviously, the particular length ofthe pencils will depend upon the size of the reactor which will dependupon the production capacity desired. Lift rods 32 and 33 may then bemanually operated by any suitable drive mechanism or, if desired, may beoperated through a servo-type system.

FIG. 1 illustrates a typical servo system in schematic fashion whereinthe source lift servo is connected to rods 32 and 33 to move the rods inan axial direction and in and out of the reactor 25 to adjust theposition of the pencil source 31 within reactor 25. Suitablethermocouples are then connected to reactor 25 and provide an inputsignal over the dotted line 41 to the source lift servo 40. In thismanner, a constant temperature can be maintained in a particular regionof reactor 25 by continuously varying the exact position of source rod31 within reactor 25 in any suitable manner.

Process feed lines, such as feed lines 50, 51 and 52, are then connectedto various regions of the reactor to supply the material to bepolymerized within the reactor and a product return line 53 extends outof the reactor 25. A typical material which may be applied to one ormore of the feed lines to 52 could be ethylene gas. Highpressure steamor some other suitable heat exchange medium may also be applied topressure jackets surrounding the reactor 25 over lines, such as lines56" and 51, in order to bring the reactor to a particular temperature(or temperature profile) required for the particular reaction which isdesired.

FIG. 2 schematically illustrates the configuration of the reactor 25 ofFIG. 1. Components similar to those of FIG. 1 are given similaridentifying numerals in FIG. 2 and throughout the application.

The reactor 25 of FIG. 2 consists of a high strength steel reactor shell60 having a top head plate 61 and a bottom head plate 62. The reactorcontains an elongated single-ended tube 63 which receives the elongatedsource 31 which is disposed concentrically within an elongated reactionchamber 64 within which the polymerization reaction (or any typereaction, in general) is to occur. Note that input and output lines arenot shown in FIG. 2, but will be described in detail hereinafter.

In order to stir or agitate the product in the reaction chamber 64 andin accordance with one feature of the invention, the chamber 64, whichencloses the radioactive source 31, receives an elongated hollow stirrerdril 65 which surrounds the source rod tube 63. Drum has paddle bladesschematically illustrated, for example, by paddle blades 66 and 67,whereby the drum 65 and the blades carried thereby are rotated in thereaction chamber 64. To this end, the lower end of the drum 65 iscarried in a bearing 68 mounted in the bottom head 62 and is connectedat its top to a stirrer shaft 69. The stirrer shaft 69 is carried inbearings 70 and 71, with the bearing 71 being contained within a motorshielding block 72 which may be of steel and is used, essentially, tocontain polymerized products below the level of the shielding block 72.

A suitable motor, schematically illustrated as motor 73, then has arotor connected to the shaft 69 and a stator connected to the body 60.Motor 73 may be of any desired type. The rotational speed of the stirrerdrum 65 can be between 120 rpm. to 3,600 rpm. An adjustment of thisrotational speed provides additional control of the temperature profilealong the reaction zone 24 and will be adjusted depending upon the typeof product which is to be manufactured.

FIGS. 3 and 4 show plan views of an actual reactor construction.

Referring to FIGS. 3 and 4, components similar to those of FIG. 2 aregiven similar identifying numerals. Thus, the elongated reactor shell 60is a cylindrical shell enclosed at its top and bottom ends by the tophead 61 and bottom head 62. The reactor, shown schematically in FIG. 3,is divided into seven reaction levels or regions and is provided withnumerous connectors for input products and the like. Thus, there areprovided connection regions along the lines and at the levels shown inFIGS. 3 and 4 (and identified by the legend alongside FIGS. 3 and 4) forconnection of thermocouples in the various thermowells. There are alsoprovided various gas inlets at the various reaction levels; a gas andpolymer outlet; and inlets and outlets to the jackets for heating thereactor vessel. There is further schematically illustrated rupture diskassemblies to which the vent stacks 28 and 29 of FIG. 1 are connectedwhereby, when the pressure within reactor 25 exceeds a particular value,these disks rupture so that the pressure can be vented through stacks 28and 29.

Referring next to FIG. 5, there is shown therein a cross-sectional viewof FIGS. 3 and 4 taken along the axis of those figures. Componentssimilar to those of the preceding figures are given similar identifyingnumerals.

FIG. 5 illustrates the reactor with the stirrer drum 89 (drum 65 of FIG.2) removed for most of its length. The reactor shell 60 of FIG. 5consists of an elongated hollow steel tube which can, for example, havean internal diameter of about 3.9 inches and a wall thickness of about2% inches. The top can 61 is fastened to the end of shell 60 by clampingflanges 90 and 91. The assembly may then be connected to any appropriatestructure for supporting the reactor. In a similar manner, the bottomhead 62 is connected to shell 60 by clamping flanges 92 and 93 which aresimilar to flanges 90 and 91, respectively. Suitable locating dowelpins, such as dowels 94 and 95, can be used for locating the top andbottom heads 61 and 62 on the shell 60. The upper end of shell 60 isprovided with an enlarged diameter 96 which contains an electrical motor73 which may be of any suitable type and which can be energized byelectrical leads brought in through openings, such as opening 97 in thetop head 61. Other openings are provided, such as openings 98 and 99 forcoolant feeds and pressure ports.

The stirrer shaft 69 is connected to the motor 73 and is mounted betweenthe schematically illustrated bearings 70 and 7-1 which may be thrustbearings for supporting the stirrer shaft 69 so that it can be rotatedwithout being axially moved.

The stirrer shaft 69 is then suitably bolted to an adapter structure1011). This adapter structure 100 is further connected to a hollowradiation rod receiving tube 101 through a suitable bearing arrangement102 where the rod receiving tube 101 extends the remaining length of thereactor and protrudes through bottom head 62.

The rod receiving tube 101 is connected to flange 121 by a suitablethread. The flange 121 is further connected to the bottom head 62 bybolts, such as bolts 121b, whereby load may be applied to seal 121a byan axial clamping action between tube 101 and the bottom head 62. Theseal 121a provides a rigid end support for the tube 101 and the pressureseal for the reaction chamber 64.

Tube 101 is an alloy steel tube having an internal diameter of about 78of an inch and an external diameter of about 1% inches. Thus, the wallthickness of tube 101 will not appreciably interfere with thetransmission of gamma radiation, but can serve to guide the motiontherethrough of the radioactive pencil or rod 31 into the reactor space.The tube 101 is solid-ended at its top, and sealed to the reactor byseal 121a where it passes through the bottom of the reactor so that thepressure in chamber 64 cannot leak into the interior of tube 101.

The main reaction chamber 64 defined between the exterior of hollow tube101 and interior diameter of shell 60 receives reactants through thevarious input connections at the various levels illustrated. Forexample, at level 5 an input channel 112 is illustrated and could beconnected to an ethylene gas line. Similar gas inlets are provided alongthe length of the reactor, as indicated by the labeled gas inlets inFIGS. 3 and 4.

A plurality of thermocouple elements or other suitable temperaturemeasuring elements are also provided as illustrated by the thermocoupledevices 111 and 113. Note that gas entries and thermocouples can beinterchanged, if desired.

An outlet channel is then illustrated as the outlet channel 115 at thebottom of the reactor and through which the output product will be takenfrom the interior of the reactor. Note, however, that output product canbe taken out at any inlet level along the length of the reactor, ifdesired, and depending upon the precise type of stirrer arrangementwhich is used. Similarly, reactant can be introduced into the reactor atchannel 115.

In order to bring the reactor to a suitable temperature, channels areformed in the outer wall of the reactor shell, such as channels 116 and117, by way of example. These channels are then connected to suitablelines connected to the fitting nipples 118- and 119 in order tocirculate steam, hot oil, cooling water, or any other suitable heattransfer media about the outer surface of reactor shell 60. The lowerend of the stirrer drum 89 is mounted on the lower end of tube 101 as bybearing 120'.

The configuration of the stirrer drum 89' is best shown in connectionwith FIGS. 6 to 10. Components similar to those of the preceding figuresare given similar identifying numerals.

Referring first to FIG. 6, the stirrer drum 89 is illustrated in oneembodiment of the invention as consisting of a hollow stainless steeldrum having an outer diameter of 2% inches and a wall thickness of inch.

The drum is mounted on adapter 100 at its upper end and over the bottombearing housing of bearing 120 at its lower end, and over the topbearing housing of bearing 102 on its upper end. A plurality of pairs ofopenings then extend along the length of the drum, which openings aredisplaced from one another by 180, with adjacent pairs of openingsrotated with respect to one another by 90 along the major portion of thelength of the drum. Each of these openings may have a diameter of 1 /2inches.

Thus, in FIG. 6 there is shown openings '130 to 140. Similar openingsare disposed on the opposite side of the stirrer drum &9 which cannot beseen in FIG. 6 which are coaxial with openings 130, 133, 134, 137 and140. Note that adjacent pairs of openings, as described above, arerotated from one another by 90 as, for example, the relationship betweenopening 130 and the adjacent pair of openings 131 and 132. The centerlines of adjacent pairs of openings are spaced by 1 inches.

-It is to be understood that the specific dimensional relationshipsgiven above may be varied by any particular type of drum stirrerconstruction and that these dimensions were used only with theillustrated embodiment of the invention. Each of the openings in thedrum, such as openings to 140, then carry welded paddles, shown aspaddles to 160, respectively. The paddles of the embodiment illustratedin FIG. 6 are disposed at an angle of 45 to the axis of the stirrer drum89 and, as shown in FIG. 10, have a pitch of 30. Note that the stirrerdrum 8-9 is to be rotated in a clockwise direction when seen in thesection of FIG. 8 so that the paddle angle is pitched backwardly intothe medium which is introduced into the reaction chamber whetherexterior or interior of the stirrer drum 89. Obviously, direction ofrotation depends on blade configuration. Further note that the bottom ofpaddles 150 to have a straight edge which cuts across a cord of thecylindrical stirrer 89, as most clearly seen in FIG. 8 for the case ofpaddle 150 and its oppositely disposed paddle 150a. The pitch and angleof the various paddles described above are again merely illustrative ofa particular paddle arrangement and other angles could be used ifdesired. Moreover, the angles of the various paddles can be changedwithin a given stirrer drum, if desired. Furthermore, the angle of thepaddles with respect to the axis 89 can be zero for all or a portion ofthe paddles, as illustrated in dotted lines 157a for the case of paddle157.

A particularly useful arrangement can be obtained where the first threeor four sets of paddles at the top of the stirrer drum are angled andpitched, as shown, for example, for paddle 150, While the remainingpaddles below this level are all pitched but parallel to the axis of thestirrer drum 89, as shown for the paddle 157a.

At the opposite ends of the stirrer drum, paddles which are parallel tothe axis of the stirrer drum are provided for the major purpose ofinsuring agitation of the medium at these end locations and to forcecirculation of the fluid media between the two annular regions and toavoid the presence of a stagnant zone.

Thus, in FIGS. 6 and 7, it can be seen that four parallel disposed butpitched paddles to 173 are provided in elongated openings 174 and 175for paddles 170 and 173, respectively. A similar arrangement is providedat the bottom of the stirrer drum, as shown in FIGS. 6 and 9 for thecase of paddles 176 to 179 where paddles 176 and 179 of FIG. 6 are shownin connection with elongated openings 180 and 181, respectively.

FIG. 6 also shows the location of various fluid inlets (or outlets itoperated in that manner) such as inlets 190, 191, 110 (previouslydescribed in FIG. 5) and 192. The drum 89 operates to divide chamber 64into two regions, shown in FIGS. 7 to 9 as external region 200 andinternal region 201. Preferably, regions 200 and 201 have the samecross-sectional area.

In operation, the rotation of the drum 89 and its various paddles willcause agitation of the gas mixture inserted into the reaction volume 64with the gas being propelled and mixed by the moving paddle wheels, suchas paddle wheels 150 to 160, and with the gas being circulated betweenthe interior volume 201 and exterior volume 200 of the reaction chamberthrough the openings in the stirrer drum, such as openings 130 to 140.It has been found that an extremely efiicient stirring action can beobtained in this manner. Moreover, it has been found that this stirringaction can be extremely well controlled by the physical placement of thestirrer drum paddles and can be controlled to obtain selective mixing atvarious levels of the reactor by controlling the angle of the variouspaddles should such selective mixing be desired.

During the mixing action, gas will be admitted into the reaction volume,for example, through inlet 192, with this gas being mixed and circulatedbetween the exterior and interior volumes 200 and 201 defined by thestirrer drum. Thus, a portion of the gas will recirculate around thedrum and through the openings for any desired number of cycles before itis ultimately discharged through a discharge opening, such as dischargeopening 115 in FIG. or any of the selected openings 110, 190 or 191 inFIG. 6. Thus, an appropriately designed stirrer paddle can operate tomaintain material within the reaction zone for any desired length oftime. Moreover, by using a source of uniformly loaded high intensityradiation, such as rod 31 which carries Cobalt 60, or any other desiredsource of gamma radiation, the radiation intensity throughout thereactor is constant and uniform for any particular radial distance fromthe rod 31. Therefore, polymerization reactions will be initiateduniformly through the reaction volume.

It will be understood that the novel apparatus of FIGS. 3 to permit theuse of a continuous process, as contrasted to a batch process and avoidsall the disadvantages which are inherent in the use of a catalystinitiated reaction where, for example, catalysts would have beeninjected into the various ports at the various levels along the reactorin the prior art. In this regard, it should also be noted that the novelstirrer drum 89 and its associated paddles and variations of paddleangles described hereinabove will operate well with a catalyst inducedreaction, although the preferred mode of operation uses the novelcentrally disposed radiation source 31 for initiating polymerizationreactions.

In one typical example of the invention, ethylene gas was injected intoports 190, 191 and 192 at an average pressure of 30,000 p.s.i. Note thatthe reactor shown herein is useful for any range of pressures up to, forexample, 45,000 psi The average temperature of reactor 60 was maintainedat 475 F. by the reaction. Steam was circulated around the exterior ofthe reactor shell 60, as described in connection with FIG. 5. A source31 was positioned within tube 101. The rate of gas flow into the reactor60 was 334 pounds per hour, and a polymerized product was withdrawn fromport 115 at the rate of 57.2 pounds per hour. The stirrer drum which canbe rotated from between 120 r.p.m. to 3,600 r.p.m. was, in this example,rotated at 3,450 r.p.m. The jacket temperature was 369 F. The reactorprovided a conversion rate of 17% with the remaining gas being cooledand recycled.

During this operation, the reactor temperature measured at the variousthermocouples, shown, for example, in FIG. 5 was observed and theposition of the rod 31 was manually controlled by withdrawing itslightly from tube 101 or inserting it deeper into tube 10 1, thereby tomaintain precribed temperatures in the reaction zone which rangedbetween 472 F. to 483 F. The average position of rod 31 was 88%inserted. As pointed out above, this operation can be automaticallyperformed by a suitable source lift servo 40 which can be located, asshown in FIG. 1. Alternately, the servo 40 may be located in the bottomof the chamber of FIG. 1, or in any other desired location.

The type of control of the rod position disclosed in the foregoing is ofgreat importance to the control of the process. Without such control,large fluctuations in production rate occur. However, by sensing thetemperature of the reaction mixture with fast acting thermocouples andmoving the radiation source rod 31 accordingly, there is, in etfect, acontrol of production rate by adjusting the fraction of the reactorvolume that is being irradiated. It should be noted that this controlmethod can be used in any continuous exothermic, adiabatic reactioninitiated by high energy radiation.

To demonstrate the novel control operation, a reactor similar to the oneof the foregoing figures, but of larger volume, is schematically shownin FIG. 11. It is assumed that the annular volume 64 has an internaldiameter of 3 inches, an outside diameter of 10.5 inches and a height of15 feet. A uniformly loaded Cobalt 60 source rod 31 having a length of15 feet is loaded into the interior of tube 101 which has a Wallthickness of about %inch.

The radiation dose rate at any point P is given by the expression:

where K=is constant,

S=source loading in curies per unit length,

b=.79'+ (.0805) (r) r in inches. [Based on a specific volume forethylene at 30,000 p.s.i. at 450 F. of .0329 tb /1b.], and

a, r, 6 0 are shown in FIG. 11.

Case A: Over the entire length of the source up to 2KSF(1r/2, b)

Case B: From 0=60 to the end of the source Case C: At the end of thesource (0 :0)

Z fi" Case A Case D: Past the end of the source Case E: More than 9 =60past the end of the source The above equations are subject to secondorder corrections which modify the results by a few percent but do notaffect the general conclusions.

FIG. 13 shows the relative production rate per unit volume (proportionalto the square root of radiation intensity) as a function of height alongthe plane halfway between the inner and outer Walls of the reactorannulus. Also plotted are the production rates as a function of heightfor the source 5% Withdrawn and 50% withdrawn. FIG. 13 shows that theeffective volume of the reactor is defined quite sharply by the axialposition of the radioactive source 31, so that there is provided anideal situation of automatically adjusting reactor size to totalproduction rate, rather than trying to control production rates in afixed size reactor. This holds for plug flow as well as back-mixedoperation, or any degree inbetween.

As a good first approximation, total production rate at a given averagetemperature is directly proportional to gas flow, and as can be seenfrom FIG. 13, the end effects are a small percentage of the radiationdistribution. Therefore, the same temperature profile and productcharacteristics will be obtained at 50% gas flow with the source 50%inserted as at design capacity with source fully inserted.

Accordingly, the reactor is controlled by varying the position of theradiation source. This has the advantage of mechanical simplicity, rapidresponse, and is easily operated by the servo 40 of FIGS. 1 and 11.

FIGS. 14 and 15 illustrate a second embodiment of the invention in whichthe source rod 31 of FIG. 2 is replaced by three independently movablesource rods 201, 202 and 203. Each of individual rods 201, 202 and 203are formed of stacked pencils of Cobalt 60 or any other suitable radioisotope and are driven by any suitable drive mechanism, schematicallyshown as drive mechanisms 204, 205 and 206, respectively. By providing aplurality of source rods, it be apparent that the relative axialpositions of the rods will vary the source intensity distribution alongthe axis of reactor 25 in any desired manner. Moreover, the distributioncan be varied merely by varying the rod positions relative to oneanother. Once a desired intensity distribution pattern is established,it is further possible to move the three rods as a unit to vary theeffective reactor volume as described previously for the singleradioactive source rod 25. Clearly, any number of parallel rods could beused. Also, in any pencil, the radioactive material need not beuniformly distributed, and the pencils in any rod need not all beequivalent.

Although this invention has been described with respect to its preferedembodiments, it should be understood that many variations andmodifications will now be obvious to those skilled in the art, and it ispreferred, therefore, that the scope of the invention be limited not bythe specific disclosure herein, but only by the appended claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows:

1. A continuously operating polymerization reactor comprising, incombination:

(a) a hollow elongated reaction chamber,

(b) means for continuously introducing polymerizable gas under pressureinto said hollow elongated chamber,

() means for continuously extracting polymerized products from saidhollow elongated chamber,

(d) means for controlling the temperature of said hollow elongatedchamber,

(e) an elongated source of high energy radiation disposed along the axisof said hollow elongated chamber,

(f) stirrer means for stirring material in the interior of said hollowelongated chamber disposed concen trically within said hollow elongatedchamber and surrounding said elongated source,

(g) and means for axially moving said elongated source into and out ofsaid chamber.

2. The reactor of claim 1 wherein said stirrer comprises a hollowrotatable drum having openings therethrough axially spaced along theaxis of said drum, and wherein said openings have paddle membersdisposed therein.

3. The reactor of claim 1 which includes a hollow tube fixed to saidelongated reaction chamber for receiving said elongated source.

4. The reactor of claim 1 wherein said hollow drum divides said hollowelongated chamber into approximately equal annular volumes.

5. A continuously operating reactor comprising, in combination:

(a) a hollow elongated reaction chamber;

(b) means for continuously introducing polymerizable gas under pressureinto said hollow elongated reaction chamber, said means comprising aplurality of gas inlets spaced along the length of the reaction chamber;

(c) a plurality of temperature measuring elements spaced along thelength of the reaction chamber and selectively interchangeable with saidgas inlets;

(d) means for continuously extracting polymerized products from saidreaction chamber;

(e) an axially located elongated hollow tube mounted within said hollowelongated reaction chamber;

(if) an elongated source of high energy radiation disposed along theaxis of said elongated hollow tube and extending through one extremityof said hollow elongated reaction chamber;

(g) stirrer means surrounding said elongated hollow tube for stirringmaterial within said hollow elongated reaction chamber, said stirrermeans comprising a drum provided with a plurality of opposed pairs ofopenings extending along the length thereof, adjacent pairs of openingsbeing oifset an angularly adjustable paddle member being mounted in eachof said openings, said stirrer means dividing said elongated reactionchamber into two annular zones, one interior and the other exterior ofsaid stirrer drum; and

(h) means connected to said elongated source of high energy radiationfor selectively positioning the inner extremity of said elongated sourceof high energy radiation at any of a plurality of locations within saidhollow elongated reaction chamber, thereby to control the productionrate of said reactor.

6. The reactor of claim 5 wherein said source is a source of gammaradiation.

7. The reactor of claim 5 which further includes temperature measuringmeans connected to said chamber and servo means connected to said meansfor positioning said elongated source and said temperature measuringmeans; said servo means moving said elongated source responsive tovariations in temperature within said chamber from a given value in adirection to maintain said temperature at said given value.

8. A continuously operating polymerization reactor comprising, incombination:

(a) a hollow elongated reaction chamber;

(b) means for continuously introducing polymerizable gas under pressureinto said hollow elongated reaction chamber, said means comprising aplurality of gas inlets spaced along the length of the reaction chamber;

(0) a plurality of temperature measuring elements spaced along thelength of the reaction chamber and selectively interchangeable with saidgas inlets;

(d) means for continuously extracting polymerized products from saidreaction chamber;

(e) an axially located single-ended elongated hollow tube mounted withinsaid hollow elongated reaction chamber, the open end of said hollow tubeproviding communication through one extremity of said hollow elongatedreaction chamber;

(f) an elongated source of high energy radiation disposed along the axisof said elongated hollow tube and extending through one extremity ofsaid hollow elongated reaction chamber;

(g) stirrer means surrounding said elongated hollow tube for stirringmaterial within said hollow elongated reaction chamber, said stirrermeans comprising a drum provided with a plurality of opposed pairs ofopenings extending along the length thereof, adjacent pairs of openingsbeing offset 90, an angularly adjustable paddle member being mounted ineach of said openings, said stirrer means dividing said elongatedreaction chamber into two annular zones, one interior and the otherexterior of said stirrer drum; and

(h) means connected to said elongated source of high energy radiationfor selectively positioning the inner extremity of said elongated sourceof high energy radiation at any of a plurality of locations within saidhollow elongated reaction chamber, thereby to control the productionrate of said reactor.

9. A continuously operating polymerization reactor as set forth in claim8 where the hollow elongated reaction chamber is provided with bearingsfor receiving the opposed extremities of the stirrer drum and a driveshaft and motor for rotating said stirrer drum are housed within saidhollow elongated reaction chamber.

10. A continuously operating polymerization reactor as set forth inclaim 8 Where said elongated source of high energy radiation isconstituted by a plurality of relatively thin elongated elements atleast one of which has a length approximately equal to the length ofreaction chamber and means connected to each of said thin elongatedelements for selectively positioning the inner ends of said elements atrespective controllable positions with respect to one another withinsaid elongated hollow tube.

References Cited UNITED STATES PATENTS 3,477,926 11/1969 Snow et a1.204--109 3,330,818 7/1967 Derby 259-40 5 FOREIGN PATENTS 8/1960 Canada17621 JOHN H. MACK, Primary Examiner 0 W. I. SOLOMON, Assistant ExaminerUS. Cl. X.R.

